From the general condition of the forcing cone, it looks like this gun has been fired a LOT. The photo isn't good enough to confirm a crack. If I were buying it, I would be very interested in B/C gap, endshake, peened cylinder notches and timing .... all the things that wear with round count. I've seen guns you could buy cheap but by the time you get them up and running reliable, you may have more bucks in it than a new gun.
It looks like the revolver may have a high round count and has seen a lot of high velocity 125gr or lighter rounds using a slow burning powder. These rounds are often referred to as "flame throwers". A lot of erosion on the inner forcing cone. I tend to stay away from revolvers that are in that condition.